Besides a history with Ryan, Maci and Mackenzie share a life-changing common connection: Both of the young women welcomed little boys when they were teenagers. But was Maci -- who had a particularly poignant moment with the future Mrs. Edwards at her wedding and shares mutual admiration with her -- caught off guard when she learned that Mackenzie has a munchkin of her own?

"I wasn't surprised to learn she was a teen mom -- I was surprised to learn how old she was [when I met her], which was 20 at the time," the Tennessean -- who enjoyed a cordial lunch with Mackenzie during tonight's Teen Mom OG episode as seen in the clip above -- recently divulged to MTV News about the now-21-year-old. "I had met her son multiple times and I knew how old he was, and I thought she was around my age because of the way she carries herself."

"She's very mature. She's got her head on her shoulders," 25-year-old Maci continued. "I was thinking, 'Hold on -- I know how old her son is, so that means if she was a teen mom, then she's way younger than me.'"

To see more of Maci and Mackenzie, be sure to keep watching Teen Mom OG every Monday at 9/8c.